The present invention relates to a method of operating a vacuum cleaner and, more particularly, to a method and apparatus for operating a vacuum cleaner which is optimally operated in accordance with the surface to be cleaned or the clogging state of the cleaner.
In a general vacuum cleaner, the input to the vacuum is constant with respect to an air flow rate irrespective of the type of surface to be cleaned. Therefore, the optimum control or the control which is comfortable to the user cannot be performed depending on the surface to be cleaned or object to be cleaned because the suction force is constantly too strong or weak.
This problem can be solved by, for instance, contolling the input in accordance with the type of surface to be cleaned, thereby adjusting the air flow rate of the vacuum cleaner. For adjusting the air flow rate of the vacuum cleaner, means for variably setting the rotational speed of the electric blower for creating the suction is first considered. Controlling the phase by using a thyristor or an inverter are known methods of varying the rotational speed of the electric blower.
The vacuum cleaner disclosed in JP-A-59-146632 belongs to the former method, in which the operating mode can be selected in accordance with the states of various kinds of floor surfaces to be cleaned.
According to the vacuum cleaner disclosed in JP-A-56-34325, it is detected that a suction port is sealed to the cleaning surface or that a filter is clogged, and thus, the rotational speed of the motor is controlled in accordance with a predetermined operation control rule (hereinafter, simply referred to as a control rule).
The foregoing Japanese official gazette (JP-A-59-146632) discloses that the operating mode can be selected in accordance with the air flow rate. However, various kinds of operating modes are set merely by adjusting an input by phase control and nothing is disclosed with respect to the optimum operation being performed by changing the fundamental characteristic of the electric blower itself. The electric blower consisting of an AC commutator motor which is used in a general vacuum cleaner has a performance characteristic as shown in FIG. 3. In the case of cleaning a bare floor surface by such a motor, when the suction port of the vacuum cleaner is sealed to the bare floor surface, the air flow rate Q decreases and a rotational speed N of the electric blower increases and the sealing force further increases, so that appropriate cleaning cannot be performed. Even if the input of the electric blower is reduced by phase control to change the characteristic as shown by a broken line in FIG. 3, no change occurs in the performance characteristic such that the rotational speed N increases with a decrease in air fow rate amount Q. Consequently, the suction port is sealed on the side of a small air flow rate similarly to the above-mentioned case and the comfortable cleaning cannot be performed.
According to the control system of JP-A-56-34325 mentioned above, control is performed in accordance using a predetermined control rule with a fixed function or gain so as to be proportional or inversely proportional to a change amount (for instance, air flow rate of an operating parameter, pressure, current, etc.) of the cleaner which changes depending on the use of the cleaner. Therefore, when the operating parameter changes, an inconvenience occurs and the contol system attempts to compensate for the inconvenience.
Such an inconvenience will now be described with reference to suction characteristic graphs shown in FIG. 12. In FIG. 12, the abscissa denotes the air flow rate Q and the ordinate indicates the rotational speed N, an electric power W, and a suction static pressure H of the electric blower. For instance, it is now assumed that the control rule is set such that when it is detected through an increase in suction static pressure H, that a curtain or the like is sucked into the suction port and the cleaner appears to be in a closed state, the rotational speed N or electric power W is controlled so as to reduce the suction static pressure H as shown by a broken line in the diagram, thereby preventing the sucking in of the curtain or the like. However, when the suction port is sealed to the carpet floor and a strong suction force is required the electric blower is contolled by the control system to reduce the suction force in a manner similar to the foregoing case, so that the necessary suction force to vacuum the carpet is not derived.
On the other hand, it is desirable to control the suction force and noises by performing such control in accordance with the wishes of a user or various kinds of use conditions such as difference between the physical strengths of persons who use (adult and child) the vacuum or the time of use. However, there is a problem such that it is impossible to perform such a proper control by a single control rule as in the conventional technique.